Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $216.46   8.574%   $235.0193   $235.02   $235.00   $235.00  
  Purchase #2 $151.57   10.808%   $167.9517   $167.95   $167.95   $168.00  
  Purchase #3 $229.63   11.593%   $256.251   $256.25   $256.25   $256.30  
  Purchase #4 $134.84   6.233%   $143.2446   $143.24   $143.25   $143.20  
  Purchase #5 $143.55   7.459%   $154.2574   $154.26   $154.25   $154.30  
  Purchase #6 $124.61   5.865%   $131.9184   $131.92   $131.90   $131.90  
  Purchase #7 $59.71   9.805%   $65.5646   $65.56   $65.55   $65.60  
  7 purchase totals = $1,060.37       $1,154.2070   $1,154.20   $1,154.15   $1,154.30